A known seat slide device disclosed in U.S. Pat. No. 5,586,740B2 includes a guide rail fixed at a vehicle floor side and extending in longitudinal direction of a vehicle seat and a slide rail fixed at a vehicle seat side to be slidably guided by the guide rail. In cross section view, the width of the seat slide device in the horizontal direction is smaller than the width of the seat slide device in the vertical direction, specifically; the form of the seat slide device is a flat form in cross section. Thus, an enough space in horizontal direction of the seat can be secured, for example, for providing an enough foot space for a rear passenger.
According to such known seat slide device, a drive member rotatably supported at the slide rail is provided outside the space formed between the guide rail and the slide rail. Thus, a driven engaging portion formed at a fixed side vertical wall of the guide rail to be engaged with the drive member is exposed toward a space under the seat.
Thus, a need exists for the seat slide device to not only secure a foot space, but also prevent the driven engaging portion from being exposed on the surface of the guide rail.